1.Field of Invention.
This invention relates to compositions of doped and co-doped Germanium-Fluorophosphate glasses for use as laser hosts and fiber amplifiers. The new and improved glass compositions are more specifically related to glasses based on or containing GeO2, Ba (PO3)2, BaO, and one of BaF2, CaF2, MgF2, PbF2 or BiF3 plus one or more dopants.
2. Description of Related Arts.
Presently, most optical glasses are manufactured in SiO2 base. These glasses have a limited infrared transmission spectra and low optical constant (refractive indices). Unfortunately, these limitations in SiO2 based glass prohibits use for more advanced applications. For example, all new fiber amplifiers need to work in a wide range infrared transmission spectrum that cannot be accomplished with SiO2 base glasses.
The existing laser fluorophosphate glasses which contain (in mass %): BaPO3F (55-66), MgF2 (15-20), Nd2O3 (1-4), Ga2O3 (9-11) were created by Russian scientists. These glasses have a limitation that is caused by a higher rate of inactive (non-active) absorption on the laser wavelength 1,064 nm that causes reduction of luminescence duration of dopant-neodymium, Patent USSR No. 471320 issued 1973.
Furthermore, transparent glasses for the infrared region based on Fluoride containing glass system PbF2-PbO-GeO2 were obtained by G. W. Cleek and E. H. Hamilton, xe2x80x9cInfrared Transmitting Germanate Glasses,xe2x80x9d U.S. Pat. No. 3,119,703 issued 1974, and systems AlF3-PbO-GeO2 by Dumbaugh, W. H., xe2x80x9cMethod of Making Infrared Transmitting Glasses,xe2x80x9d U.S. Pat. No. 3,531,305 issued 1976. However, these glasses have a very limited domain of glass formation between GeO2 and Fluorides.
The general structure of glasses on a germanium fluorophosphates base is described in xe2x80x9cGermanate Glasses: Structure, Spectroscopy and Propertiesxe2x80x9d, by A. Margaryan and M. Piliavin, publishes by Arthek House, Boston and London, 1993. This treatise describes such glasses using infrared methods of measurement of glass properties. However, the book does not describe or provide compositions of specific glasses.
Other existing laser glasses on a phosphate base containing methaphosphates of Li, Na, K, Mg, Ca, Sr, Cd, Ba, Pb, and phosphates of elements Al and Zr, B, Ce, trivalent neodymium Nd3+ and trivalent ytterbium Yb3 were developed by I. M. Buzhinsky, et al., U.S. Pat. No. 3,846,142. These glasses are characterized by high specific energy stored by Yb3+ in the active element at a section of stimulated emission of at least 2.5xc3x9710xe2x88x9221 cm2. However, these type of glasses have a limited infrared transparency. Fluorophosphate glasses also have been formed on Al(PO3)3, NaPO3, P2O5 and fluorides AlF3, ZrF4, LiF, NaF, MgF2, CaF2, BaF2, LaF3, LnF3 base by L. J. Andrews and W. J. Miniscalco, U.S. Pat. No. 4,962,995. These compositions are recommended for high efficiency Er3+ doped optical fiber lasers, amplifiers and super luminescent sources.
Heavy metal oxide glass optical fibers on GeO2, TeO2, Sb2O3, PbO, Bi2O3, Al2O3, P2O5, Al(PO3)3, M(PO3)2 where M is Mg, Ca, Ba or Sr and NPO3 where N is Li, Na or K were created by D. C. Tran, U.S. Pat. No. 5,796,903, and U.S. Pat. No. 5,274,728. The most preferred are those based on GeO2. These glasses are recommended for use in laser medical surgery.
The publication on xe2x80x9cFluorine-Containing Germanate Glassesxe2x80x9d A. A. Margaryan, Wai Min Lui. Journal of Material Science Letters, Vol. 11, No 22, Nov. 15, 1992, pp 1511-1513 gives a description of glass formation domain and density between RGe4O9xe2x80x94RF2 systems. However, this publication does not include or describe the new ingredients such as: Ba(PO3)2, PbF2, BiF3 and fluorides or oxides of rare elements Nd2O3(NdF3), Er2O3(ErF3), Yb2O3(YbF3), Ho2O3(HoF3), Pr2O3(PrF3), Tm2O3(TmF3), Tb2O3(TbF3), MnO(MnF2) of this new invention.
Another publication xe2x80x9cSynthesis of Glasses in Germanium Fluorophosphate; Systemsxe2x80x9d A. A. Margaryan, S. S. Karapetyan Mater, Resp. Soveshch. Neorg. Khim. 5th, 1977 pp.54-5 describes only the glass formation domain of germanium fluorophosphates systems BaGe4O9xe2x80x94Ba(PO3)2xe2x80x94RF2 where R only includes Mg, Ca, Sr, Ba. However, these formulations do not include any compositions with rare earth dopants and other fluorides, such as PbF2, BiF3.
The patent xe2x80x9cGermanium Oxide Based Glass Compositionxe2x80x9d by Sakaguchi, Shigeki, Patent No. 08012370 JP discloses glasses for near infrared ray transmission optical fiber, having a composition which is improved in stability to crystallization and reduced Rayleigh scattering in GeO2xe2x80x94P2O5xe2x80x94MFx systems. However, this composition of glass is not doped with rare earth elements and may be used only for passive optics. Additionally, this glass system is different from the present invention system BaGe4O9xe2x80x94Ba(PO3)2xe2x80x94RFx composition.
This invention is related to germanium-fluorophosphate glass compositions, which are used for laser hosts and fiber amplifiers.
Progress in the optical industry is measured in the creation and manufacturing of new more efficient types of optical glasses. The glasses based on germanium dioxide and phosphates offer many advances over crystalline matrices. Germanium dioxide based glasses have a higher refractive index and dispersion than glasses with silicon dioxide. Germanium dioxide glass index of refraction is (nD=1.6068) and it can be used as a basis for creating special flints that possess higher refractive indices. The high infrared transparency of germanium dioxide allows its use as an essential element in fiber optics technology. Glass-phase GeO2 is transparent as an optical medium in the important spectral region from 0.280 to 5 micron.
In germanium fluorophosphate systems, the range of glass formation increases in the following order BaF2 greater than SrF2 greater than CaF2 greater than MgF2, which shows the increasing strength of the cation field. In comparison, this behavior is the opposite of alkaline earth oxide containing systems. Magnesium fluoride containing glasses are especially distinct in their ability to form glasses with up to 80-85 mol% of MgF2 concentration.
The above-mentioned phenomenon also contributes to formation of the elemental cell structure of germanium fluorophosphate melt. The general features of the infrared spectra show the existence of superimposed spectra of germinates, metaphosphates and orthophosphates or the radicals Me(O,F)6 and MeF4. Intense lines are observed between the wavelength numbers 900-800 cmxe2x88x921, 1,300-1,000 cmxe2x88x921, and 650-400 cmxe2x88x921. The bands in the region of 900-800 cmxe2x88x921 are due to Gexe2x80x94Oxe2x80x94Ge in (GeO4)4xe2x88x92. The maximal of bands within 1,300-1,000 cmxe2x88x921 are due to oscillations of PO2, POP in the metaphosphate ion (PO3)n1xe2x88x92. Detected bands by groups of the types Me(O,F)6, MeF4, and PO2 in metaphosphate or tetrametaphosphate anions, are responsible for the bands in the region 650-400 cmxe2x88x921.
When increasing the concentration of Ba(PO3)2 in melt, the Gexe2x80x94Oxe2x80x94Ge band shifts in the direction of higher frequencies in exchange for RGe4O9.
Glasses that contain 50-60 mol % Ba(PO3)2 have fluorophosphates and germanium phosphate as structural forming components. The bands of Gexe2x80x94Oxe2x80x94P are found in the regions 1,110-1,100 cmxe2x88x921 and 1,070-1,050 cmxe2x88x921. This creates the formation of germanium orthophosphate structures, Ge3(PO4)4. Glasses containing more than 60 mol % Ba(PO3)2 are formed by fluorophosphate and pure germanate components. Fluoride containing germanium phosphate glasses are formed from structural elements of the form (GeO4)4xe2x88x92, (PO3)n1xe2x88x92, Gexe2x88x92(xe2x88x92Oxe2x88x92Pxe2x88x92) Me(O,F)6 or (MeF4)2xe2x88x92.
Germanium fluorophosphate glasses are effective and efficient in the process of creation of laser hosts and amplifiers. These glasses have a high spectral transparency in the ultraviolet (UV), visible (VIS) and infrared (IR) frequencies. There is a possibility of including a high concentration of dopants: to 20-25 wt % for fn elements (rare-earth elements), and to 40-50 wt % for dn elements (transition elements), which is significantly higher than crystalline materials high concentration of dopants 1-5 wt %. Phosphor and germanium content glasses were chosen for the following reasons: They have a large glass-forming region, they can be used as a host with fluorine ions, and they show good thermo-mechanical and chemical properties.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.